[danmar]

Yeah, the new 2.5L 4-cylinder has a very bizarre EGR system in it that, I think, is designed to not cut down on power like most EGR systems do, but it's turned out to be a basketcase

EGR(Exhaust Gas Recirculation) is designed to reduce the NOX emissions, by cooling down the combustion chambers, not to cut down on power.
The EGR kicks in at about 1500 RPM controlled by engine vacuum and reroutes a small amount of exhaust gases back into the cylinder chambers thus cooling down the combustion chambers, thus reducing the NOX(nitrous oxide).

Nissan's issue most likely was that the cars failed smog test due to high amount of NOX, created in part by partially plugged up EGR pass ways.

[JamesP81]

EGR(Exhaust Gas Recirculation) is designed to reduce the NOX emissions, by cooling down the combustion chambers, not to cut down on power.

I know it's not designed to cut down on power, but when you recirculate exhaust gas into the cylinders like that it certainly has that effect. Having read about the design of that engine, I suspect they were trying to find a way to reduce NOX emissions without the normal cut in power and efficiency that goes with that.